The improvement of foundry coatings to enhance performance is important. This paper investigates the effect of using sol‐gel component as an additive to foundry coatings applied on chemically bonded sand cores. Three parameters at three levels each were investigated using Taguchi experimental parameter design. The effects of the sol‐gel component on viscosity, density, °Baumé, core coverage and permeability are shown. Numerical simulations were used to predict defect areas. The thermal profiles of the core materials during casting were determined, and the surface quality of the castings was evaluated. The results show that the surface quality of castings obtained by adding the sol‐gel component to the coatings for cold box cores has no significant difference from castings produced with coatings without sol‐gel component. On the other hand, the addition of the sol‐gel component in coatings for furan cores showed significant improvement on the surface quality of the castings compared to that obtained without sol‐gel component.